1. Field of the Invention
The present invention relates to an electronic programmable switch lever control timer that can activate a switch lever arm directly and automatically at preselected adjustable intervals of time to provide for programmable control of the power provided to the load normally controlled from the switch.
2. Description of the Prior Art
Several types of electronic programmable switch timers are available in the market place and many more types have been described in U.S. patent applications. Most, however, can be characterized as falling into one of two major categories, first, those devices that control the switch lever directly and, second, those devices that replace the switch altogether with another type of device. For example, U.S. Pat. No. 5,828,018 dated Oct. 27, 1998, U.S. Pat. No. 5,306,957, dated Apr. 26, 1994, U.S. Pat. No. 5,465,031 dated Nov. 7, 1995, and U.S. Pat. No. 5,719,362 dated Feb. 17, 1998 fall into the first category. U.S. Pat. No. 5,397,930, dated Mar. 14, 1995, U.S. Pat. No. 6,531,836 B2, dated Mar. 11, 2003, U.S. Pat. No. 5,898,240 dated Apr. 27, 1999, U.S. Pat. No. 5,473,204 dated Dec. 5, 1995, U.S. Pat. No. 4,354,120 dated Oct. 12, 1982, and U.S. Pat. No. 6,121,889 dated Sep. 19, 2000 all fall into the second category.
Those electronic switch timer devices that fall into the second category have several significantly limiting characteristics: a) the use of a power triac or an electrical relay for controlling the flow of power, b) the existing electrical switch has to be removed and electrical rewiring is necessary, and c) the use of the 60 Hz power line voltage for providing the requisite time alignment for the program timer control means.
Limitations associated with the use of a power triac include inefficiency from power dissipation within the device and the requisite need for heat sinking, likely failure modes that make it difficult to obtain U.L. listing, restrictive limitations on the minimum and maximum power loads that can be controlled, and limitations on the type of load that can be controlled. Limitations associated with the use of an electrical relay are cost, the type of load that can be controlled and the maximum current that the load utilizes but its use is not as restrictive as a thryristor.
A major disadvantage of the embodiments in the second category is the need for the removal of the existing switch mechanism and its replacement with the device described in the referenced embodiments. Electrical rewiring of the existing AC wiring is necessary.
The main limitation associated with the using the 60 Hz power line voltage as the basis for keeping track of time is that of losing timing and/or accuracy of program timing as a result of the absence of the 60 Hz power signal due to power main failure/interruption and to inadvertent removal. To overcome this disadvantage, a battery-backup system has to be added to the device such that the time alignment can draw on this as a power source when needed.
Of the four patents that fall into the first category, the first, U.S. Pat. No. 5,828,018 dated Oct. 27, 1998, relates to a cover plate for a light switch with a housing that contains a rack gear system with a spring-loaded mechanical drive assembly. A standard wall switch can be activated and deactivated for a fixed length of time as determined by the amount of time to relax a helical spring that is tightened by the initial activation of a lever that extends outward from the housing. The timing is purely mechanical and is activated and deactivated as a single event. Once the lever is manually activated to turn on the wall switch, the timing mechanism is initiated and after a fixed period of time the spring mechanism deactivates the wall switch. This operation is repeated only by the manual activation of the extension lever arm. The object of this device is to allow a wall switch to be activated, for example, to turn on a hallway light and then after a fixed period of time, have the wall switch turned off to allow the hallway light to be off. This device is meant for allowing temporary, short-term activation of a wall switch and then deactivation for energy saving purposes. This device must be initiated manually.
The second patent that falls into the first category, U.S. Pat. No. 5,306,957, dated Apr. 26, 1994, relates to a device that fits over a standard wall switch cover plate with a housing that contains a slide device to engage the switch and a lever arm that extends outward from the housing to manually operate the slide to engage the standard wall switch. The housing further has a latching and catching means to retain the slide to one end of its slide path thereby keeping the wall switch in an activated position. While moving the slide, a spring means is loaded for the return action. There is also a latching release means to retract the latch from the catch means thereby releasing the slide device and allowing the slide to travel to the other end of its slide path thereby keeping the wall switch in the deactivated position. The linear travel of the slide is initially activated manually with the use of the lever arm. The latch release means comprises an electromechanical device such as a solenoid to retract the latch from the catch. The spring means then returns the slide to its original position and the wall switch is deactivated. It also mentions that a microprocessor can be used in the timing function for the release of the slide mechanism and there is an optional time interval selector for presetting a selected time interval for the timer. The timing cycle is initiated manually by movement of the slide and the device automatically executes the rest of the cycle.
The two above referenced patents that fall into the first category also have some common limitations. The significant common limitations of the two patents are mechanical complexity, each timing On-Off cycle has to be manually initiated, manual initiation of the start of the cycle is by actuation of an external lever arm, and multiple On and Off time cycles cannot be pre-programmed and initiated automatically but have to be separately initiated and programmed.
The third patent that falls into the first category, U.S. Pat. No. 5,465,031 dated Nov. 7, 1995 relates to a self-contained programmable actuator, which can be mounted directly onto the outside of the faceplate of a standard wall switch having a built-in light dimmer. The actuator can be programmed to adjust the position of the dimmer's mechanical control arm in accordance with a program that repeats on a daily basis. The actuator includes two small batteries, a miniature electric motor with a gear/linkage mechanism and an actuator frame operable to engage with and to move the dimmer's mechanical control arm over its complete range. The amount of travel of the actuator frame is controlled by the use of a switch means to count the number of rotations of the control shaft. Rotation of the motor in one direction is achieved by using a battery with one polarity. Rotation of the motor in the opposite direction is achieved by using a second battery with the opposite polarity. The device is mounted to the wall switch plate by the use of adhesive tape. Further, it is stated that upon removing the device from the switch faceplate, it may be necessary to replace the adhesive tape before re-mounting the device. For manual actuation of the dimmer switch, several keypads on the front panel must be removed to allow access to the dimmer switch.
The above referenced patent has several limitations. The gear/linkage mechanism is complex and no means is discussed by which the gear/linkage mechanism can properly and accurately engage with the switch lever arm during its installation. The amount of travel of the actuator frame has to be controlled by the use of switches and rotational counting means. Separate battery supplies are needed to allow different directions of rotation of the motor. In addition, the device is attached to the switch cover plate by the use of adhesives which may not be secure and which may have an effectiveness that decreases with age. Also, the adhesive tape may have to be replaced when removing the device from the wall switch faceplate. Such a removal operation may be necessary when there is a need to replace the batteries.
The fourth patent that that falls into the first category, U.S. Pat. No. 5,719,362 dated Feb. 17, 1998 relates to a device that fits over a standard wall switch cover plate with a housing that contains a DC motor, elliptically shaped cam, gears, and a slide plate to activate the wall toggle switch. The device is attached to the wall plate by first removing one screw of the wall plate. The device in then placed over the wall plate and the screw hole opening of the device is aligned with the hole of the screw removed from the wall plate. A longer screw is then inserted and tightened to hold the device to the wall plate. In attaching the device to the wall plate, the toggle switch arm is allowed to protrude through an opening in the slide plate. To activate the wall switch, a DC motor rotates an elliptically shaped cam which provides linear motion in an upward direction to the slide plate. The slide plate then moves the toggle switch to its up position. To deactivate the wall switch, the DC motor continues to rotate in the same direction and the elliptically shaped cam provides linear motion in a downward direction to the slide plate. The slide plate then moves the toggle switch to its down position. The amount of rotational motion must be precisely controlled to allow the slide plate to move to its extreme position of travel and to prevent the slide plate from reversing direction, moving towards its previous position and away from the desired extreme position of travel. The amount of rotational motion of the cam is controlled by the use of limit switches, one at each extreme position of travel of the slide plate. Mechanical manual override of the wall switch is achieved by first rotating a circular disk that surrounds the wall switch toggle to a position that disengages the wall switch toggle from the slide plate. The wall switch toggle arm can then be moved to its desired position.
The above referenced patent has several limitations. First, the gear/linkage mechanism is complex and the amount of rotational motion must be precisely controlled. Limit switches are used to determine the amount of rotation of the elliptical cam gear. Second, the device is secured to the standard wall plate by the use of only one screw. The means for manually operating the wall switch is not direct and takes several operations.